Polyoxyalkylene block copolymers are well known to those skilled in the non-ionic surfactant art. Specifically, U.S. Pat. No. 3,740,421 (Schmolka) assigned to BASF discloses aqueous gels prepared using a block copolymer of polyoxyethylene/polyoxypropylene suitable for pharmaceutical and personal care compositions. U.S. Pat. No. 3,639,574 (Schmolka) assigned to BASF discloses polyoxyethylene/polyoxypropylene block copolymers as gelling agents for hydrogen peroxide compositions. U.S. Pat. No. 4,465,663 (Schmolka) assigned to BASF discloses polyoxybutylene/polyoxyethylene block copolymers as gelling agents for aqueous gels useful in personal care and pharmaceutical applications. These compounds are sold by the BASF Corporation under the PLURONIC.RTM. tradename.
Additionally, U.S. Pat. No. 4,272,394 and U.S. Pat. No. 4,411,810 disclose the use of polyoxyalkylene block copolymers in machine dishwashing applications. U.S. Pat. No. 4,925,988 discloses a nonionic surfactant employing a specific combination of alkanol, ethylene oxide and propylene oxide useful in an automatic dishwashing application. U.S. Pat. No. 5,374,368 describes the use of liquid EO/PO/EO triblock co-polymers (PLURONIC.RTM. L 31 and L 35 surfactants) in stable hydrogen peroxide releasing dental care compositions at levels of 55-90% by weight of the dental care composition. U.S. Pat. No. 3,740,421 discloses gel forming solid EO/PO/EO triblock copolymers useful in cosmetic and personal care formulations at levels of approximately 20-25% by weight. Preferred solid EO/PO/EO triblock copolymers have a molecular weight of 4,600-16,000. Said solid EO/PO/EO triblock copolymers form a gel when added to an aqueous solution. U.S. Pat. No. 3,867,533 discloses aqueous gel compositions containing solid EO/PO/EO triblock copolymers, having a molecular weight of 6,450-20,000 useful at levels of approximately 20% by weight. Said compositions are useful in preparing cosmetic formulations. U.S. Pat. No. 4,465,663 discloses clear aqueous cosmetic gels containing solid EO/BO(butylene oxide)/EO triblock copolymers at levels of approximately 20%. U.S. Pat. No. 5,035,880 discloses a stable dentifrice compositions containing a cetylpyridinium bactericide and EO/PO/EO solid triblock copolymers (PLURONIC.RTM. F 127 surfactant), and polyethylene glycol at levels of 15-80% by weight. U.S. Pat. No. 4,476,107 discloses a mouthwash containing EO/BO(butylene oxide)/EO triblock copolymers at levels of 0.5-5.0% by weight. U.S. Pat. No. 5,057,307 discloses oral hygiene gels containing non-ionic surfactants, coating substances; and viscosifiers. Said non-ionic surfactants are the PLURONIC.RTM. F 108 and F 127 surfactants available from BASF Corporation, Mt. Olive, N.J. U.S. Pat. No. 5,256,396 discloses a topical composition comprising an EO/PO/EO solid triblock copolymer (PLURONIC.RTM.) F 127 surfactant) used at a level of more than 10% to about 17% by weight. EPO-546-627A discloses mouthwash compositions comprising solid EO/PO/EO triblock copolymers such as PLURONIC.RTM. L 108, F88 surfactants at levels of 0.5-3% by weight. U.S. Pat. No. 5,073,368 discloses mouthwashes containing solid EO/PO/EO triblock copolymers such as PLURONIC(.RTM. F 87 surfactant at levels of 0.1-3% by weight. WO 93/13750 discloses an ocular cleansing composition comprising solid PLURONIC.RTM. F 87 and paste PLURONIC.RTM. P 85 EO/PO/EO triblock copolymers. PLURONIC(.RTM. P 85 surfactant is 4-9% by weight of the cleansing composition, PLURONIC.RTM. F 87 surfactant is 0.5-2% by weight of the cleansing composition. Finally, U.S. Pat. No. 5,096,698 discloses a dental creme composition containing a non-ionic triblock liquid EO/PO/EO copolymer or a solid triblock EO/PO/EO copolymer at levels of 0.1-5% by weight. Said copolymers help to prevent phase separation. PLURONIC.RTM. F 108 surfactant (solid) is most preferred, followed by PLURONIC.RTM. F 87, PLURONIC.RTM. F 127, and PLURONIC.RTM. L 72 surfactants. U.S. Pat. No. 4,272,394 discloses novel, low-foaming nonionic surfactant for machine dishwashing compositions. U.S. Pat. No. 4,411,810 discloses a low foaming, low cloud point, nonionic surfactant for machine dishwashing compositions. JP 47-48366 B4 discloses a process for producing tasteless, liquid, heteric polyoxyalkylene compounds of molecular weight 1000 or higher. U.S. Pat. No. 5,187,191 discloses polyoxyalkylene block copolymers in agricultural formulations. U.S. Pat. No. 5,496,542, U.S. Pat. No. 5,374,368, and U.S. Pat. No. 5,424,060 disclose the use of polyoxyalkylene compound for formulating a stable percarbonate formulation as well as a dentrifice composition.
The present invention relates to oral care compositions, such as dentrifice formulations. Dentrifice formulations typically contain substantial amounts of humectants. Humectants help the formulation retain its moisture, thus, preventing the formulation from hardening when the container cap is left open for extended periods. Typical humectants employed in such formulations are glycerol, sorbitol which are usually the preferred humectants because of their sweet taste. Other humectants which are also used are polyethylene glycols of low molecular weight typically between 200-600. Liquid polyethylene glycols constitute an excellent choice as a carrier for formulating a non-aqueous, dentrifice formulation since they come with several advantages such as good hygroscopicity, low viscosity, good compatibility with several dentrifice ingredients, low volatility, low cost, low toxicity, low odor and low pour point. More recently, toothpaste compositions are being formulated without any significant incorporation of water. Examples of such toothpaste compositions are those that cannot tolerate the presence of significant levels of water due to concerns related to decomposition of key ingredients leading to loss of activity, or reactivity of ingredients, for example, baking soda and a peroxygen compound such as, hydrogen peroxide or sodium percarbonate. The formulation and increased stability of such toothpaste compositions is achieved by employing a non-aqueous carrier typically selected from low molecular weight liquid polyethylene glycols. Dentrifice formulations also contain an anionic surfactant, typically selected from sulfate esters of C.sub.10-18 alcohols. An example of such a anionic surfactant is sodium lauryl sulfate. The primary function of the anionic surfactant is to provide efficient foaming action during brushing. However, in many instances the foaming action provided by the anionic surfactant alone is inadequate and often additional ingredients have to be added in combination with the anionic surfactant to achieve the desired foam profile during brushing. A common ingredient that is typically selected to achieve additional foam boosting are the high molecular weight, solid block copolymers of ethylene oxide and propylene oxide. Examples of such solid block copolymers are those that have a number average molecular weight over 8000 and also contain at least 50% ethylene oxide. Particularly preferred are those that contain between 70%-80% ethylene oxide and have a number average molecular weight greater than 9000.
Further, a limitation also exists with the use of the high molecular weight, solid, block copolymers of ethylene oxide and propylene oxide in a non-aqueous dentrifice formulation because they are insoluble in the liquid polyalkylene glycol carrier. Dissolution of the solid block copolymer in the liquid polyalkylene glycol carrier is achieved by heating the two components until a single clear phase is achieved. Unfortunately, upon cooling back to ambient temperatures, the solid block copolymer has a tendency to phase separate leading to the formation of a heterogenous mixture. The formation of a heterogenous phase is particularly problematic since it may lead to a preferential partitioning of certain dentrifice components in any one phase and an altering of the homogenity of the formulation. This altering of the homogenity of the formulation is particularly noticeable when the dentrifice formulation undergoes multiple heating and cooling cycles during transportation and storage.
The Applicants have solved these aforementioned problems in the art. Surprisingly, Applicants have discovered that if the solid block copolymers are rendered liquid during their preparation, by addition of small amounts of a C.sub.3 or higher alkylene oxide to the crystalline, hydrophilic portion of the solid block copolymer to produce a liquid polyoxyalkylene compound of similar hydrophilicity and molecular weight, then a single, clear, homogenous phase is achieved upon adding to the liquid, polyoxyalkylene glycol carrier. An additional advantage with the use of the high molecular weight liquid polyoxyalkylene compounds of this invention is that upon addition to the polyalkylene glycol carrier, they are readily miscible and form a clear, homogenous, single phase composition, and do not have to be heated to achieve dissolution.